Add "Find missing numbers" kata

Author: juan-antonio-ledesma

7-kyu/find-missing-numbers.md

@@ -0,0 +1,42 @@
+<h1>Find missing numbers <sup><sup>7 Kyu</sup></sup></h1>
+
+<sup>
+  <a href="https://www.codewars.com/kata/56d02e6cc6c8b49c510005bb">
+    <strong>LINK TO THE KATA</strong>
+  </a> - <code>ARRAYS</code> <code>FUNDAMENTALS</code>
+</sup>
+
+## Description
+
+You will get an array of numbers.
+
+Every preceding number is smaller than the one following it.
+
+Some numbers will be missing, for instance:
+
+```
+[-3,-2,1,5] //missing numbers are: -1,0,2,3,4
+```
+
+Your task is to return an array of those missing numbers:
+
+```
+[-1,0,2,3,4]
+```
+
+## Solution
+
+```javascript
+const findMissingNumbers = nums => {
+  const minNumber = Math.min(...nums)
+  const maxNumber = Math.max(...nums)
+
+  const missingNumbers = []
+
+  for (let i = minNumber + 1; i < maxNumber; i++) {
+    if (nums.indexOf(i) === -1) missingNumbers.push(i)
+  }
+
+  return missingNumbers
+}
+```

README.md

@@ -151,6 +151,7 @@ JavaScript katas on Codewars are programming challenges that help you improve yo
 - **[Exes and Ohs](./7-kyu/exes-and-ohs.md)**<br><sup>`FUNDAMENTALS`</sup>
 - **[Factorial](./7-kyu/factorial.md)**<br><sup>`FUNDAMENTALS`</sup>
 - **[Find Count of Most Frequent Item in an Array](./7-kyu/find-count-of-most-frequent-Item-in-an-array.md)**<br><sup>`DATA STRUCTURES` `FUNDAMENTALS`</sup>
+- **[Find missing numbers](./7-kyu/find-missing-numbers.md)**<br><sup>`ARRAYS` `FUNDAMENTALS`</sup>
 - **[Find The Duplicated Number in a Consecutive Unsorted List](./7-kyu/find-the-duplicated-number-in-a-consecutive-unsorted-list.md)**<br><sup>`ARRAYS` `ALGORITHMS`</sup>
 - **[Find the next perfect square!](./7-kyu/find-the-next-perfect-square.md)**<br><sup>`ALGEBRA` `FUNDAMENTALS`</sup>
 - **[Find the stray number](./7-kyu/find-the-stray-number.md)**<br><sup>`FUNDAMENTALS` `ALGORITHMS`</sup>